The production of metal ingots by the electroslag remelting (ESR) process is now well established, particularly in relation to alloys such as nickel-base alloys, stainless steels, tool steels, etc. where metal cleanliness is especially important. The ESR process comprises providing a mold, which may be water-cooled, may be open at each end and is usually clamped to a stool so as to complete the mold structure. To initiate remelting, a molten slag is introduced into the bottom of the mold and a consumable electrode is introduced into the molten slag usually with power on. Conductivity of the slag is such that passage of melting current in the electrode-mold circuit through the slag promotes rapid heating and surface melting of the electrode. Molten metal droplets from the electrode drop downward through the molten slag and collect in the bottom of the mold to form a new remelt ingot as melting of the consumable electrode proceeds. The ingot size producible by ESR has considerable latitude and ingots of 60 inches diameter and greater are produced commercially at present.
The consumable electrode must, of course, be initially provided, usually by casting as an ingot. The ingot to form the electrode is itself a heavy metal piece. For example, in one commercial installation, a 34 inch diameter cast electrode is employed in producing a 40 inch diameter ingot by ESR.
It is of course necessary to establish an electrical connection to the electrode, since a holder or arbor of standard size is provided in the ESR furnace to hold the electrode. Since the electrode will usually be large, a metal stub is usually fastened to one end of the electrode, as by welding or other suitable means. Generally, the stub is a metal piece of heavy rectangular section. In order to provide a good weld connection between stub and electrode, it has been the practice to cut off an end of the ingot intended to form the electrode as by sawing, machining, etc. to provide a planar surface matching a planar surface of the stub. Since a large piece of metal is involved, metal wastage and high cutting or machining costs are entailed. Thus, in a commercial installation, annual costs amounting to $90,000 were encountered as a result of the cutoff operation.